Fail if system.file() is supplied path starting with inst

Closes #104

NEWS.md

@@ -1,5 +1,9 @@
 # pkgload (development version)
 
+* The `system.file()` shim now fails if you supply a path that starts
+  with `inst` to better reproduce the behaviour with installed
+  packages (#104).
+
 * `load_all()` now imports its dependencies lazily to avoid parallel
   installation issues (#89).
 

R/shims.r

@@ -66,6 +66,15 @@ shim_system.file <- function(...,
   # be installed. To fully duplicate R's package-building and installation
   # behavior would be complicated, so we'll just use this simple method.
 
+  if (dots_n(...) && is_string(..1)) {
+    if (is_string("inst", ..1) || grepl("^inst/", ..1)) {
+      cli::cli_abort(c(
+        "Paths can't start with `inst`",
+        i = "Files in `inst` are installed at top-level."
+      ))
+    }
+  }
+
   pkg_path <- find.package(package)
 
   # First look in inst/

tests/testthat/_snaps/shim.md

@@ -0,0 +1,19 @@
+# system.file() fails if path starts with `inst` (#104)
+
+    Code
+      (expect_error(shim_system.file("inst/WORDLIST", package = "pkgload", mustWork = TRUE))
+      )
+    Output
+      <error/rlang_error>
+      Error in `shim_system.file()`:
+      ! Paths can't start with `inst`
+      i Files in `inst` are installed at top-level.
+    Code
+      (expect_error(shim_system.file("inst", "WORDLIST", package = "pkgload",
+        mustWork = TRUE)))
+    Output
+      <error/rlang_error>
+      Error in `shim_system.file()`:
+      ! Paths can't start with `inst`
+      i Files in `inst` are installed at top-level.
+

tests/testthat/test-shim.r

@@ -115,3 +115,14 @@ test_that("Replacement system.file returns correct values when installed", {
 test_that("division operator is not interpreted as a path (#198)", {
   expect_null(dev_topic_find("/"))
 })
+
+test_that("system.file() fails if path starts with `inst` (#104)", {
+  expect_true(
+    is_string(shim_system.file(package = "pkgload", mustWork = TRUE))
+  )
+
+  expect_snapshot({
+    (expect_error(shim_system.file("inst/WORDLIST", package = "pkgload", mustWork = TRUE)))
+    (expect_error(shim_system.file("inst", "WORDLIST", package = "pkgload", mustWork = TRUE)))
+  })
+})